Actually it looks like it won't affect too many people. If you take the Red Line to and from games, they will be rerouting them to the Green Line elevated. You'll still be able to board the Red Line at any station north of the construction and essentially take the train right to the park's front door. Looks like the only people who really get boned in all of this are people who live in Chinatown. When's that Green Line stop at Cermak supposed to be done?
Map from the CTA: http://www.transitchicago.com/redsouth/